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<p class='vspace'></p><h2>if  (conditional)  and   ==,  !=,  &lt;,  &gt; (comparison operators)</h2>
<p><strong><code>if</code></strong>, which is used in conjunction with a comparison operator, tests whether a certain condition has been reached, such as an input being above a certain number. The format for an if test is:
</p>
<p class='vspace'></p><pre>if (someVariable &gt; 50)
{
  // do something here
}
</pre>
<p class='vspace'></p><p>The program tests to see if someVariable is greater than 50. If it is, the program takes a particular action. Put another way, if the statement in parentheses is true, the statements inside the brackets are run. If not, the program skips over the code.
</p>
<p class='vspace'></p><p>The brackets may be omitted after an <em>if</em> statement. If this is done, the next line (defined by the semicolon) becomes the only conditional statement.
</p><pre>

if (x &gt; 120) digitalWrite(LEDpin, HIGH); 

if (x &gt; 120)
digitalWrite(LEDpin, HIGH); 

if (x &gt; 120){ digitalWrite(LEDpin, HIGH); } 

if (x &gt; 120){ 
  digitalWrite(LEDpin1, HIGH);
  digitalWrite(LEDpin2, HIGH); 
}                                 // all are correct

</pre>
<p class='vspace'></p><p>The statements being evaluated inside the parentheses require the use of one or more operators:
</p>
<p class='vspace'></p><h3>Comparison Operators:</h3>
<pre> <strong>x == y</strong> (x is equal to y)
 <strong>x != y</strong> (x is not equal to y)
 <strong>x &lt;  y</strong> (x is less than y)  
 <strong>x &gt;  y</strong> (x is greater than y) 
 <strong>x &lt;= y</strong> (x is less than or equal to y) 
 <strong>x &gt;= y</strong> (x is greater than or equal to y)
</pre>
<p class='vspace'></p><h4>Warning:  </h4>
<p>Beware of accidentally using the single equal sign  (e.g.<code> if (x = 10)</code> ). The single equal sign is the assignment operator, and sets x to 10 (puts the value 10 into the variable x).  Instead use the double equal sign (e.g.<code> if (x == 10) </code>), which is the comparison operator, and tests <em>whether</em> x is equal to 10 or not. The latter statement is only true if x equals 10, but the former statement will always be true.
</p>
<p class='vspace'></p><p>This is because C evaluates the statement <code> if (x=10) </code> as follows: 10 is assigned to x (remember that the single equal sign is the <a class='wikilink' href='Assignment.html'>assignment operator</a>), so x now contains 10. Then the 'if' conditional evaluates 10, which always evaluates to TRUE, since any non-zero number evaluates to TRUE. Consequently,  <code>if (x = 10)</code> will always evaluate to TRUE, which is not the desired result when using an 'if' statement. Additionally, the variable x will be set to 10, which is also not a desired action.
</p>
<p class='vspace'></p><p><strong>if</strong> can also be part of a branching control structure using the <a class='wikilink' href='Else.html'>if...else</a>] construction.
</p>
<p class='vspace'></p><p><a class='wikilink' href='index.html'>Reference Home</a>
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<p class='vspace'></p><p><em>Corrections, suggestions, and new documentation should be posted to the <a class='urllink' href='http://arduino.cc/forum/index.php/board,23.0.html' rel='nofollow'>Forum</a>.</em>
</p>
<p class='vspace'></p><p>The text of the Arduino reference is licensed under a
<a class='urllink' href='http://creativecommons.org/licenses/by-sa/3.0/' rel='nofollow'>Creative Commons Attribution-ShareAlike 3.0 License</a>.  Code samples in the reference are released into the public domain.
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